TITLE:
Catalytic Hydrothermal Liquefaction of Water Hyacinth Using Fe3O4/NiO Nanocomposite: Optimization of Reaction Conditions by Response Surface Methodology
AUTHORS:
Godwin Aturagaba, Dan Egesa, Edward Mubiru, Emmanuel Tebandeke
KEYWORDS:
Catalytic Hydrothermal Liquefaction, Water Hyacinth, Bio-Oil, Central Com-posite Design, Response Surface Methodology, Optimization
JOURNAL NAME:
Journal of Sustainable Bioenergy Systems,
Vol.13 No.3,
July
31,
2023
ABSTRACT: This
research aimed at optimizing the reaction conditions for the catalytic
hydrothermal liquefaction (HTL) of water hyacinth using iron oxide/nickel oxide
nanocomposite as catalysts. The iron oxide/nickel oxide nanocomposite was
synthesized by the co-precipitation method and used in the hydrothermal
liquefaction of water hyacinth. The composition and structural morphology of
the synthesized catalysts were determined using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning
electron microscopy (SEM), and atomic absorption spectroscopy (AAS). The
particle size distribution of the catalyst nanoparticles was determined by the
Image J software. Three reaction parameters were optimized using the response
surface methodology (RSM). These were:
temperature, residence time, and catalyst dosage. A maximum bio-oil
yield of 59.4 wt% was obtained using iron oxide/nickel oxide nanocomposite
compared to 50.7 wt% obtained in absence of the catalyst. The maximum bio-oil
yield was obtained at a temperature of 320°C, 1.5 g of catalyst dosage, and 60
min of residence time. The composition of bio-oil was analyzed using gas
chromatography-mass spectroscopy (GC-MS) and elemental analysis. The GC-MS
results showed an increase of hydrocarbons from 58.3% for uncatalyzed
hydrothermal liquefaction to 88.66% using iron oxide/nickel oxide
nanocomposite. Elemental analysis results revealed an increase in the hydrogen
and carbon content and a reduction in the Nitrogen, Oxygen, and Sulphur content
of the bio-oil during catalytic HTL compared to HTL in absence of catalyst
nanoparticles. The high heating value increased from 33.5 MJ/Kg for uncatalyzed
hydrothermal liquefaction to 38.6 MJ/Kg during the catalytic HTL. The catalyst
nanoparticles were recovered from the solid residue by sonication and magnetic
separation and recycled. The recycled catalyst nanoparticles were still
efficient as hydrothermal liquefaction (HTL) catalysts and were recycled four
times. The application of iron oxide/ nickel oxide nanocomposites in the HTL of water
hyacinth increases the yield of bio-oil and
improves its quality by reducing hetero atoms thus increasing its energy
performance as fuel. Iron oxide/nickel oxide nanocomposites used in this study
are widely available and can be easily recovered magnetically and recycled.
This will potentially lead to an economical, environmentally friendly, and
sustainable way of converting biomass into biofuel.